Method of treating steel making slags



Patented Jan. 14, 1936 UNITED STATES METHOD OF TREATING STEEII MAKINGSLAGS Augustus B. Kinzel, Douglaston, N. Y., assignor to ElectroMetallurgical Company, a corporation of West Virginia PATENT OFFICE NoDrawing. Application August 17, 1934 Serial No. 740,204. 1

5 Claims.

The present invention relates to metallurgical slags, and moreparticularly to methods of treating steel melting slags to improve thecharacteristics thereof.

It is common practice in open hearth steel practice to add fiuorspar tothe molten bath in order to increase the fluidity of the slag. 'Whilethe exact physico-chemical mechanism of this thinning process is notknown, the effect of adding fluorspar is to increase the fluidity of theslag for a short time only after the addition, the slag gra'duallybecoming thicker again, so that the net efiect of the fluorspar additionis of a temporary nature.

Another disadvantage inherent in the addition of fluorspar to steelfurnace slags is due to the marked cutting or destructive action of theslag thus treated upon the furnace lining.

An object of this invention is to thin the slag 30. The mean thicknessof the resulting layer of slag was then measured to give an index ofviscosity; The above procedure was then repeated, adding 5% and 10%,respectively, of zirconia ore of the following compositionas determinedby analysis:

Z1O2: 73.8%; SiOz: 19.48%; TiOz: 0.61%;

Of the compounds mentioned above, all but ZrOz and TiOz are usuallycontained in open hearth steel slags. As may be seen from the tablebelow, the addition of zirconia ore has a very marked efiect on the slagviscosity, and as little as 5% ore addition markedly thins the slag.This is true not only of the slags taken from the plain carbon steelheats at two stages of operation, but also of the slag taken from thechrome steel heat.

Additions Temperature, S18 late Origin of slag Slag remarks oi zirconiad centithigkgess Fluidity ore grade Percent Inches Pittsburghsteel Pigg0.25% 0 None. 1435 Fairly fluid.

1).. an 5 1435 4o Fluid. D do 10 1435 $5 Very fluid. Wheeling steelPlain low 0 bath. None. 1460 y Fairly fluid.

Do 5 1421 at. Fluid. Do do 10 1443 M Do. Pittsburghcrucible.chlromesteelladle None. 1505 1 Viscous.

s ag. Dn rin 5 1509 its Fairly fluid. Do do 10 1513 36 Very fluid.

oi open hearth steel furnaces in a permanent I claim:

manner.

Another object of this invention is to prevent or minimize thedestructive action of steel furnace slags upon the furnace lining.

These and other objects of this invention are accomplished in accordancewith this invention by using a flux containing zirconia (Zr-Oz) and/ortitania (Ti02) as addition material to open hearth furnace slags. Inpracticing one embodiment of this invention, three samples of ordinaryopen hearth steel furnace slag were used. Two pounds of each of thesamples were melted in a magnesite-lined crucible and heated to thetemperatures shown in the sub-joined table. The temperature in each casewas selected to give slag of viscosity corresponding to that. found innormal operation. The temperatures were measured with an opticalpyrometer, suitable stirring and other precautions being taken.Following the temperature determination the slag was poured upon a steelplate inclined at an angle of 1. Method of improving the workingcharacteristics of basic open hearth steel slags which comprises addingto said slags a substantial proportion of zirconium oxide, whereby thefluidity of said slags is permanently increased to a considerable degreewhile at the same time their cutting action on the hearth and lining ofthe furnace is decreased.

2. Method of improving the working characteristics of basic open hearthsteel slags which comprises adding to said slags a substantial propor-'tion of zirconium oxide and titanium oxide, whereby the fluidity of saidslags is permanently increased to a considerable degree while at thesame time their cutting action on the hearth and lining of the furnaceis decreased.

3. Method of improving the working characteristics of basic open hearthsteel slags which comprises adding to said slags more than about 3% andless than about 10% of zirconium oxide in the form of mineral materialcontaining essensaid slags is permanently increased to a considerabledegree while at the same time their cutting action on the hearth andlining of the furnace is decreased.

4. Method or improving the working characteristics of basic open hearthsteel slags which comprises adding to said slags more than about 3% andless than about 10% of zirconium oxide and titanium oxide in the form ofmineral material containing essentially zirconium oxide and titaniumoxide, whereby the fluidity of such slags is permanently increased to aconsiderable degreev tially zirconium oxide, whereby the fluidity or,

on the hearth and lining of the furnace is de- 10 creased.

' AUGUSTUS B. KINZEL.

